The happy news fulfills a longtime wish for the Duke and Duchess of Cambridge, both of whom have been vocal from the very beginning of their marriage -- and even before then -- about their desire to start a family together. In 2010, shortly after getting engaged while on holiday in Kenya, East Africa, the couple opened up about their plans for children.

"I hope we'll be able to have a happy family ourselves," Middleton said at the time. "[The royal family has] been great over the years, helping me with difficult times, and we see a lot of each other, and they're very, very dear to me."

"I think we'll take it one step at a time. We'll sort of get over the marriage thing first and then look at kids," the prince chimed in. "But obviously we want a family. So we'll have to start thinking about that."

It seems they've been thinking about it ever since. Just two months after walking down the aisle, Middleton appeared to have babies on the brain during a visit to Quebec's Freedom of the City Ceremony in July 2011.

The Duchess showed a hint of her maternal side while chatting with 2-year-old Raffaela and her dad, David Cheater, who wished the newlywed well in her efforts to have children of their own. In response, Middleton said, "Yes, I hope to."

Prince William has expressed similar hopes. In September, he told onlookers at the Gardens by the Bay attraction in Singapore that he wanted two kids with his wife. And earlier, in May, he told Katie Couric that he was considering leaving the military to focus full-time on his duties as a husband and -- eventually -- as a father.

"I'm still trying to decide. It's a really difficult one because I really enjoy my time in the Air Force," he revealed during ABC's Jubilee Queen special. "But the pressures of my other life are building, and fighting them off or balancing the two of them has proven quite difficult. More importantly, I'd rather like to have children."

He added: "I'm just very keen to have a family and both Catherine and I are looking forward to having a family in the future."

Indeed, the royal lovebirds have seemed increasingly baby-crazy in recent months. At a reception in April to celebrate the Scott Amundsen Centenary Race to the South Pole, for example, the Duke and Duchess had eyes only for a 3-week-old boy named Hugo.

"Kate and William cooed over Hugo," an observer told Us. "Both of them were commenting [on] how cute the baby was and they were both googly-eyed."